What is a vortex flowmeter?

A vortex flowmeter is a flowmeter designed based on the Karman vortex street principle. It is used to measure the flow velocity and accumulated flow of fluids (liquids, gases, and steam) in pipelines.

1. Working Principle
Kármán vortex street principle: The core principle is to infer flow velocity by using the vortex frequency generated when a fluid flows through a triangular prism of a specific shape. (Click here for more information on vortex flow meter.)

2. Core Structure

Meter body: The part that connects to the pipeline.

Vortex generator (bluff): The core component that generates the vortex street.

Sensor: Detects vortex frequency and converts tiny pressure or vibration changes into electrical signals.

Signal converter and display: Amplifies, filters, and shapes the sensor signal to calculate the flow rate and display it.

3. Main Features

Advantages:

Versatile: Can measure liquids, gases, and steam, but is particularly well-known for steam measurement.

No moving parts: Simple and robust construction, high reliability, and minimal maintenance.

Moderate accuracy: Typical accuracy is ±1.0% R.

Wide range: High turndown ratio of 10:1.

Universal output signal: Pulse signal, 4-20mA, RS485, or HART are available.

High temperature and pressure resistance: Suitable for a wide temperature and pressure range, up to 330°C.

Selection Guide - How to Choose a Vortex Flowmeter?

1. Identify Key Operating Parameters
Measured Medium: Identify the type of liquid, gas, or steam (e.g., saturated steam, superheated steam, compressed air, water, etc.).

Flow Range: Maximum flow rate, minimum flow rate, and typical flow rate.

Medium Temperature: Maximum/Minimum Operating Temperature (°C).

Medium Pressure: Maximum/Minimum Operating Pressure (MPa or Bar).

Medium Density: Density under operating conditions (especially for gases and steam). For steam, identify whether it is saturated steam or superheated steam.

Medium Viscosity: Dynamic viscosity of the liquid (mPa·s). Vortex flowmeters are suitable for low-viscosity media (typically <10 mPa·s).

2. Determine Instrument Specifications (Core Technology Selection)

Meter Diameter: DN15-1500mm

Connection Method:

Flange Connection: Standards include GB, HG, ANSI, and DIN.

Clamp Connection: Suitable for small diameters, medium- and low-pressure applications, and easy to install.

Threaded Connection: Primarily used for small diameters (DN15-DN50).

Instrument Material:

Instrument Body Material: Commonly carbon steel, 304 stainless steel, or 316 stainless steel. Select based on the corrosiveness of the media and the pressure rating.

Shedder and Sensor Material: Typically 304 or 316 stainless steel; Hastelloy alloy may be used for corrosive media.

Pressure Rating: Select based on the system's maximum operating pressure (e.g., PN 1.6 MPa, PN 4.0 MPa, Class 150, etc.), with a safety margin.

Temperature Rating: Confirm the medium temperature range that the instrument's sensor and converter can withstand.

3. Select Output and Function (to meet system requirements)

Output Signal:

Pulse Output: Used for cumulative flow or high-frequency response applications, offering high accuracy.

4-20 mA Analog Output: Most commonly used for remote display and control of instantaneous flow.

RS485 / HART / PROFIBUS-PA / MODBUS: For digital communication, enabling remote parameter setting and diagnostics, and are standard features of smart meters.

On-site Display: Whether a local LCD display is required for viewing instantaneous and accumulated flow rates.

Power Supply:

24VDC/220VAC

Explosion-proof and Protection Rating:

If used in flammable and explosive environments, select an explosion-proof model, such as Ex d IIC T6 Gb (flameproof) or Ex ia IIC T6 Ga (intrinsically safe).

Protection Rating: The sensor is typically IP65, and the converter is IP65 or IP67. For outdoor or humid environments, select a higher protection rating.

4. Evaluate the Installation and Environment (to ensure stable operation)

Mounting Orientation: When measuring liquids, install horizontally or vertically (full pipe); when measuring gases or steam, vertical installation with the flow direction upward is recommended.

Straight Pipe Requirements: Critical! Generally, 10D in front and 5D in the back are required (D is the pipe diameter). If there are flow disruptors such as pumps, valves, or elbows upstream, a longer straight pipe section or the installation of a flow conditioner is required. Insufficient installation space is a common cause of inaccurate measurements.

Ambient Vibration: Assess the vibration conditions on site. If vibration is severe, select a model with good vibration resistance (modern digital signal processing technology has greatly improved vibration resistance) or implement vibration reduction measures such as pipe reinforcement.

Ambient Temperature and Humidity: Ensure that the operating temperature of the converter is within the allowable range.